RAID5 for Linux

[mark at buttery.org (Mark J. Dulcey)]

Bob Keyes wrote:
> At my new job, we have a NAS "Snap Appliance", which is pretty horrible
> and I want to get rid of it. So I am going to push for a Linux solution.
> I'd want RAID level 5, and Serial ATA drives, and of course linux
> niceness. I was looking at the Adaptec 2810SA, but it's got 8 ports..I
> though you needed 9 for RAID5 (one for each bit plus one parity) or am I
> misunderstanding this? I'd also want hot-swappable. Anyone have any
> suggestions?

RAID 5 can be done with various numbers of drives. The Linux software 
RAID support, for instance, works with any number >= 3. You can read 
about that at http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html

Of course, you're looking at a hardware product rather than software 
RAID. However, the requirements should be similar. The Adaptec data 
sheet says that card supports "up to 8 SATA drives"; that phrase implies 
that it will also work with a smaller number. The data sheet, alas, is 
vague about exactly how many you DO need.

As for hot-swapping, the card handles it, but you'll also want some sort 
of way of mounting the drives to facilitate swapping. (Opening up a 
typical tower box, unscrewing drives, etc. probably isn't what you have 
in mind.) I don't have any suggestions there, but I'm sure somebody on 
the list will.